There is currently great interest in optical fibers that can be used in mid-infrared (MIR) applications, such as the delivery of quantum cascade lasers. While silica optical fibers are commonplace and easy to obtain, such fibers have a limited window of wavelengths at which they are transparent and are highly absorbing of MIR light. Chalcogenide (ChG) glasses, on the other hand, are transparent across the entire infrared (IR) spectrum. While ChG can be used to produce optical fibers, ChG is extremely brittle and it is therefore difficult to produce robust ChG fibers.
Although silica fibers are made by drawing a preform in the ambient environment, ChG fibers cannot be produced in this manner because they are sensitive to the environment and oxidize easily. Instead, ChG fibers are typically produced by melting two ChG glasses (one for the core and one for the cladding) in a protected environment and drawing a fiber from a nozzle in a manner in which one glass surrounds the other. Once the fiber has been drawn, a thin polymer jacket can be applied. While this manufacturing method is feasible, it is difficult to maintain a uniform draw for long lengths (e.g., over 10 m) of the ChG glasses using the method because they are so soft during the draw process. In addition, it can be difficult to apply the polymer jacket because of the fragility of the ChG glass. Furthermore, because the polymer jacket is thin, the ChG optical fiber end product is quite fragile. Moreover, because of the conditions required to make the fiber, ChG optical fibers are extremely expensive.
From the above discussion, it can be appreciated that it would be desirable to have a way to produce robust ChG optical fibers with greater ease.